Luis Felipe Hinojosa

Sensitivity of leaf size and shape to climate: global patterns and paleoclimatic applications

• Paleobotanists have long used models based on leaf size and shape to reconstruct paleoclimate. However, most models incorporate a single variable or use traits that are not physiologically or functionally linked to climate, limiting their predictive power. Further, they often underestimate paleotemperature relative to other proxies. • Here we quantify leaf-climate correlations from 92 globally distributed, climatically diverse sites, and explore potential confounding factors. Multiple linear regression models for mean annual temperature (MAT) and mean annual precipitation (MAP) are developed and applied to nine well-studied fossil floras. • We find that leaves in cold climates typically have larger, more numerous teeth, and are more highly dissected. Leaf habit (deciduous vs evergreen), local water availability, and phylogenetic history all affect these relationships. Leaves in wet climates are larger and have fewer, smaller teeth. Our multivariate MAT and MAP models offer moderate improvements in precision over univariate approaches (± 4.0 vs 4.8°C for MAT) and strong improvements in accuracy. For example, our provisional MAT estimates for most North American fossil floras are considerably warmer and in better agreement with independent paleoclimate evidence. • Our study demonstrates that the inclusion of additional leaf traits that are functionally linked to climate improves paleoclimate reconstructions. This work also illustrates the need for better understanding of the impact of phylogeny and leaf habit on leaf-climate relationships.

Estimation of temperature and precipitation from morphological characters of dicotyledonous leaves

The utility of regression and correspondence models for deducing climate from leaf physiognomy was evaluated by the comparative application of different predictive models to the same three leaf assemblages. Mean annual temperature (MAT), mean annual precipitation (MAP), and growing season precipitation (GSP) were estimated from the morphological characteristics of samples of living leaves from two extant forests and an assemblage of fossil leaves. The extant forests are located near Gainesville, Florida, and in the Florida Keys; the fossils were collected from the Eocene Clarno Nut Beds, Oregon. Simple linear regression (SLR), multiple linear regression (MLR), and canonical correspondence analysis (CCA) were used to estimate temperature and precipitation. The SLR models used only the percentage of species having entire leaf margins as a predictor for MAT and leaf size as a predictor for MAP. The MLR models used from two to six leaf characters as predictors, and the CCA used 31 characters. In comparisons between actual and predicted values for the extant forests, errors in prediction of MAT were 0.6°-5.7°C, and errors in prediction of precipitation were 6-89 cm (=6-66%). At the Gainesville site, seven models underestimated MAT and only one overestimated it, whereas at the Keys site, all eight models overestimated MAT. Precipitation was overestimated by all four models at Gainesville, and by three of them at the Keys. The MAT estimates from the Clarno leaf assemblage ranged from 14.3° to 18.8°C, and the precipitation estimates from 227 to 363 cm for MAP and from 195 to 295 cm for GSP.

Cambios climáticos y vegetacionales inferidos a partir de paleofloras cenozoicas del sur de Sudamérica.

espanolSe presenta una reconstruccion del clima continental del sur de Sudamerica, sobre la base de un analisis fisionomico foliar de 15 tafofloras, provenientes en su mayoria de yacimientos de Chile y Argentina. A partir de las estimaciones climaticas obtenidas y la composicion fitogeografica, se postula la sucesion temporal de cuatro nuevas paleofloras: Gondwanica; Subtropical Gondwanica; Mixta; y Subtropical Neogena. Los resultados indican que las tafofloras del Cenozoico se asocian a por lo menos tres escenarios climaticos contrastantes : 1- condiciones tropicales relacionadas a un evento calido y humedo del Paleoceno/Eoceno, asociadas a las Paleofloras Gondwanica y Subtropical Gondwanica; 2- cambio hacia condiciones mas templadas y secas hacia el final del Eoceno y principios del Oligoceno, relacionado con el evento de enfriamiento global del limite Eoceno/Oligoceno (consecuencia de la glaciacion Antartica). Durante este tiempo habria imperado la Paleoflora Mixta; 3- finalmente, durante el Mioceno un nuevo evento calido humedo, durante el cual la temperatura media anual aumento entre 6 y 9°C comparado con el periodo anterior. Este periodo de calentamiento esta relacionado con el optimo climatico del Mioceno Medio y se caracteriza por el desarrollo de la Paleoflora Subtropical Neogena. EnglishA reconstruction of the continental climate of southern South America, based on physiognomic analyses of fifteen taphofloras, coming mainly from Chile and Argentina, is presented here. Based on the climate estimates and the phytogeographical composition of the Cenozoic paleofloras analyzed, the succession of four new Paleofloras is proposed: Gondwanic; Subtropical Gondwanic; Mixed and Subtropical Neogene Paleoflora. The results indicate that these paleofloras are, at least, related with three major paleoclimatic scenarios: 1- Paleocene/Eocene, warm and humid tropical conditions, associated with both Gondwanic and Subtropic Gondwanic Paleofloras; 2- a climate shift towards temperate-drier conditions at the end of the Eocene and early Oligocene, related with the cold global event of the Eocene-Oligocene boundary (as a consequence of the onset of Antarctic glaciation). Time where Mixed Paleofloras dominated, and 3- finally, a warm and humid event again occurred during the Miocene, during this time, mean annual temperature was 6-9°C warmer than for the previous period. This warm event is related with the mid Miocene climatic optimum and it is characterized by the development of Neogene Subtropical Paleoflora.

Genetic evidence for glacial refugia of the temperate tree Eucryphia cordifolia (Cunoniaceae) in southern South America

PREMISE OF THE STUDY The temperate forests of southern South America were greatly affected by glaciations. Previous studies have indicated that some cold-tolerant tree species were able to survive glacial periods in small, ice-free patches within glaciated areas in the Andes and in southern Patagonia. Here we asked whether populations of the mesothermic species Eucryphia cordifolia also were able to survive glaciations in these areas or only in unglaciated coastal areas. METHODS The chloroplast intergenic spacer trnV-ndhC was sequenced for 150 individuals from 22 locations. Genetic data were analyzed (standard indexes of genetic diversity, a haplotype network, and genetic differentiation) in a geographical context. KEY RESULTS Two of the nine haplotypes detected were widespread in high frequency across the entire range of the species. The highest levels of genetic diversity were found around 40°S, decreasing sharply northward and more moderately southward. No differences in genetic diversity were found between Andean and coastal populations. Notably, seven haplotypes were found in a small area of the Coast Range known as the Cordillera Pelada (40°S). The differentiation coefficients G(ST) and N(ST) revealed that most of the genetic variation detected was due to variation within populations. CONCLUSIONS The low levels of population differentiation and the high genetic diversity found in the Cordillera Pelada suggest that this area was the main refugium for E. cordifolia during glaciations. Nevertheless, given the high levels of genetic diversity found in some Andean populations, we cannot discount that some local populations also survived the glaciation in the Andes.

Finding patterns of distribution for freshwater phytoplankton, zooplankton and fish, by means of parsimony analysis of endemicity

Durante las ultimas decadas, los estudios limnologicos en sistemas chilenos han contribuido al conocimiento de la composicion de especies y de las principales variables ambientales de muchos cuerpos de agua distribuidos sobre un amplio intervalo latitudinal, desde los 18o a los 53o S. Asimismo, aun carecemos de una vision comprensiva acerca de la estructura y funcionamiento de las aguas dulces regionales. En este trabajo revisamos la informacion sobre la biota pelagica de las cuencas de Chile, con el proposito de revelar patrones de distribucion de especies y su posible asociacion con variables ambientales. Construimos matrices de presencia-ausencia para fitoplancton, zooplancton y peces en lagos y cuencas. Desde esta base de datos, realizamos analisis de parsimonia de endemismo, como medio para determinar patrones fundamentales de distribucion de la biota dulceacuicola. Tambien, determinamos la relacion entre la presencia de especies y algunas variables relevantes de los sitios. Nuestros resultados sugieren que la latitud ejerce una fuerte influencia en la distribucion de especies, aunque tambien la altitud, longitud y el area ejercen efectos significativos en algunos grupos. Por otro lado, los resultados sugieren una relacion entre el grado de vagilidad de los grupos y el grado de estructuracion de la metacomunidad, relacionada con el numero de areas de endemismos.

Variability of water relations and photosynthesis in Eucryphia cordifolia Cav. (Cunoniaceae) over the range of its latitudinal and altitudinal distribution in Chile

The aim of this study was to investigate, during the summer of the year 2008, the variation in leaf water and photosynthetic characteristics of Eucryphia cordifolia Cav. (Cunoniaceae) along its broad latitudinal distribution in central south Chile (36 degrees to 42 degrees S). The latitudinal variation in water potential (Psi(w)), water potential at saturation (Psipi(sat)), water potential at the turgor lost point (Psipi(tlp)), stomatal density of the leaves, leaf nitrogen concentrations and photosynthetic light response were studied in eight populations. The populations located in the northern region of the distribution of E. cordifolia had the lowest leaf water potential. Osmotic potential at full turgor was highest in the two southernmost populations and gradually decreased towards the northernmost points. Similarly, osmotic potential at zero turgor was the lowest in the northern population. On the contrary, the symplastic water content was lower in the two southernmost populations. The highest net photosynthesis rate was recorded for plants in the populations of intermediate distributions, and it was dependent on the precipitation and temperature gradient. The northern populations, which are subject to the lowest precipitations, showed the lowest stomatal densities, which were tightly linked with stomatal conductance variation. Therefore, the variability of A(max) was independent of stomatal density and conductance, so that the northern populations, subject to environments with less water availability, presented higher photosynthetic water use efficiency. Photosynthesis variations were also not associated with changes in leaf water potential or in nitrogen content in E. cordifolia leaves, which did not show any consistent latitudinal or altitudinal trend. In conclusion, the results support our hypothesis that the leaf water relations, stomatal characteristics and photosynthetic rates of the leaf would vary along its latitudinal gradient, helping to explain the ability of E. cordifolia trees to inhabit a broad latitudinal and altitudinal range throughout the central south Chile.

Influence of Soil Chemical Variables and Altitude on the Distribution of High-alpine Plants: the Case of the Andes of Central Chile

Abstract Temperature is one of the major abiotic factors influencing distribution and productivity of alpine plant species. Although some edaphic parameters (e.g. soil acidity) have also been suggested as determinants in the spatial distribution of alpine vegetation, there is little background on the importance of soil chemical properties in altitudinal gradients, particularly in the high Andes. The present study determined whether soil chemical properties affect spatial distribution and abundance of alpine plants in an altitudinal gradient in the Andes of central Chile, emphasizing metal content. A direct gradient analysis took place at Yerba Loca Natural Sanctuary (YLNS), based on a geobotanical sampling conducted in 73 sites distributed from 1970 to 3330 m a.s.l. According to a Canonical Correspondence Analysis, the main soil chemical factors that explain the pattern of compositional variation of high Andean vegetation are, besides altitude, total soil copper (Cu) content, percentage of soil organic matter, and available phosphorus and nitrogen. An analysis of shoot Cu content conducted in 19 plant species found in sites with highest soil Cu contents (>250 mg kg−1) showed high levels of Cu in their shoots (>100 mg kg−1). These results demonstrate species or ecotypes with optimal distribution in soils with high Cu contents, such as Armeria maritima, Trisetum lasiolepis, and Montiopsis potentilloides, which may have tolerance to this metal.

Testing for functional convergence of temperate rainforest tree assemblages in Chile and New Zealand

ABSTRACT An important tenet of biogeography and comparative ecology is that disjunct assemblages in similar physical environments are functionally more similar to each other than to assemblages from other environments. Temperate rainforests in South America, New Zealand and Australia share certain physiognomic similarities, but we are not aware of any statistical evidence that these disjunct plant assemblages share a distinctive suite of functional traits, or trait combinations. We compiled height, leaf, wood and reproductive traits from the 25 commonest arborescent species at Chilean and New Zealand sites matched for summer rainfall, summer maximum temperatures, and winter minimum temperatures. We then used multivariate tests of trait convergence. Tropical and subtropical assemblages served as out-groups. PERMANOVA showed convergence of trait centroids at the two temperate sites, where trees on average had denser wood and smaller leaves than trees at the (sub)tropical sites. Principal components analyses carried out separately on each assemblage showed that the Chilean and New Zealand assemblages were also the most similar pair in terms of trait relationships, although New Zealand also shared strong similarities with subtropical Argentina. The main axis of variation in both temperate assemblages ranged from small, short-lived understorey trees with soft leaves, to emergents with sclerophyllous leaves and fairly dense wood. However, the New Zealand assemblage was much richer in small trees with soft leaves than its Chilean counterpart; possible historical influences on this difference include conditions favouring radiation of small trees during the late Neogene in New Zealand, competition from Chusquea bamboos in Chile and the historical absence of browsing mammals from New Zealand. Environmental filtering has produced similar values of individual traits in Chile and New Zealand, but only partial convergence of functional trait combinations. As far as we know, this is the first study to statistically test whether disjunct tree assemblages on climatically matched sites are more functionally similar to each other than to assemblages from other environments.

A climatic and taxonomic comparison between leaf litter and standing vegetation from a Florida swamp woodland.

One method to determine past climate has been the use of leaf morphological characteristics of fossil leaves quantified using modern climate and canopy leaf characteristics. Fossil assemblages are composed of abscised leaves, and climate may be more accurately determined by using leaves from leaf litter instead of the canopy. To better understand whether taphonomic processes make a difference in this relationship, a north-central Florida woodland was sampled to determine the morphologically based climate estimates from these leaves. Leaves from woody, dicotyledonous plants were collected and identified, then compared using presence/absence data and analyzed using several linear regression equations and the CLAMP data set. Although the majority of standing vegetation was reflected in leaf litter, some inconsistencies were observed, which may reflect plant community structure or sampling technique. Mean annual temperature (MAT) and growing season precipitation (GSP) were estimated from leaf litter morphological characters and living leaves. Overall, values for MAT estimated from litter and living leaves were cooler than actual MATs, although several accurate and high estimates were obtained depending on the predictive method used. Estimated GSP values were higher than actual GSPs. Statistically, no difference was observed between MAT and GSP estimates derived from leaf litter vs. estimates derived from living leaves, with one exception.

Quantitative Analysis of Cenozoic Palynofloras from Patagonia, Southern South America

The statistical analysis of published Paleocene-Late Miocene palynological data from Patagonia supports several major stages of vegetation. These stages represent distinctive floral assemblages, both in composition and structure. Detrended correspondence analysis shows that during the Paleocene, southern South America was dominated by Australasian, Neotropical and Pantropical phytogeographical elements (Gondwanic paleoflora). The climate was warm and very humid. The Early Eocene was dominated by Neotropical and Pantropical taxa (Subtropical Gondwanic Paleoflora) and a reduced proportion of Australasian and a low proportion of Antarctic elements. The Middle Eocene and Oligocene were characterized by the ‘Mixed Paleoflora’ with the exception of the Sloggett Formation. The climate was less humid due to the onset of the Antarctic glaciation. The presence of Antarctic palynomorphs (Nothofagaceae, Podocarpaceae, Proteaceae) in Patagonia is consistent with the global cooling trend during the Late Eocene and Early Oligocene. By the Late Oligocene-Early Miocene, warm climates allowed the southward dispersal of Neotropical elements (palms, Cupania, Alchornea, Rubiaceae, Combretaceae), adding megathermal elements to the local Gondwanic floras. The appearance of some Neotropical families (Symplocaceae, Euphorbiaceae Alchornea) may indicate the Late Oligocene global warming event. The rise of xerophytic and halophytic shrubby-herbaceous elements (Convolvulaceae, Asteraceae, Poaceae, Chenopodiaceae and Ephedraceae) during the Late Oligocene, becoming more abundant during the Early Miocene began to give a modern appearance to plant communities. The Early-Middle Miocene corresponds to the Transitional Paleophytogeoprovince of central and southeastern Argentina, defined by a mix of Neotropical and Austral components. The Middle—Late Miocene was characterized by the final demise of megathermal elements in Patagonia, coupled with an increasing diversity and abundance of xerophytic adapted taxa, including Asteraceae, Chenopodiaceae and Convolvulaceae. Late Miocene vegetation was similar to the present vegetation, with the steppe expanded across extra-Andean Patagonia and the forest restricted to western areas where rainfall was still abundant.